Nitric oxide, decomposition chlorine

By following the pressure change, Ashmore and Spencer studied both the decomposition of nitrosyl chloride at 523 and 573°K and the combination of nitric oxide and chlorine at temperatures from 430 to 573°K. In the case of nitrosyl chloride decomposition, the initial rate law can be written as... 

The gas-phase reaction of nitric oxide with chlorine has received a great deal of attention. Very often it has been studied concurrently with its reverse, the decomposition of nitrosyl chloride, viz. 

Physical properties of hexachloroethane are Hsted in Table 11. Hexachloroethane is thermally cracked in the gaseous phase at 400—500°C to give tetrachloroethylene, carbon tetrachloride, and chlorine (140). The thermal decomposition may occur by means of radical-chain mechanism involving -C,C1 -C1, or CCl radicals. The decomposition is inhibited by traces of nitric oxide. Powdered 2inc reacts violentiy with hexachloroethane in alcohoHc solutions to give the metal chloride and tetrachloroethylene aluminum gives a less violent reaction (141). Hexachloroethane is unreactive with aqueous alkali and acid at moderate temperatures. However, when heated with soHd caustic above 200°C or with alcohoHc alkaHs at 100°C, decomposition to oxaHc acid takes place. 

The hydride is frequently obtained by partial decomposition of arsine, as by the atmospheric oxidation of an aqueous solution,2 or by the influence on the gas of the silent electric discharge.3 Gaseous arsine may also undergo decomposition by the prolonged action of air,4 chlorine,5 nitric oxide,6 nitric or sulphuric acid,7 mercuric chloride 8 or phosphorus pentaehloride.9 In the last case the reaction may be represented by the equation ... 

The work by Ashmore and co-workers on the nitric oxide-chlorine system has already been mentioned in the context of reactions of nitric oxide with molecular halogens. It was first suggested in 1953 by Ashmore and Chanmugam10 that the second-order molecular mechanism for the thermal decomposition of nitrosyl chloride might be accompanied by a radical mechanism at higher temperatures, which they envisioned as... 

When a mixture of chlorine and NOC1 (in N2) was flash photolyzed through a Pyrex filter (to suppress NOC1 photolysis) appreciable NOC1 decomposition occurred57. The nitric oxide was observed in absorption but with virtually no excitation. The reaction is... 

Ashmore, P. G., and J. Chanmugam Reactions in the system hydrogen, chlorine, nitric oxide, and nitrosyl chloride. Part 2. — The thermal decomposition of nitrosyl chloride. Trans. Faraday Soc. 49, 265 (1953). 

Greater than equilibrium concentrations of intermediate species have been observed in the combustion products of several reactant systems. Examples are the concentrations of ammonia in the products of the decomposition of hydrazine (32), the concentration of CH4 in ethylene oxide decomposition (33), nitric oxide and ammonia in the products of the reaction of hydrazine and nitrogen tetroxide (34), and chlorine monofluoride in the products of the reaction of hydrazine and chlorine pentafluorlde (35). 

To measure temperatures locally requires the use of a fine-wire thermocouple rather than a resistance thermometer. (A rapid respmise, and hence accurate reading, is only achieved with the most delicate of junctions however, the increased fragility imposes a genuine limit on the practical size of junction whidi may be used.) Gerri and Kaufman were able to work with 0.001" (25 / m) Pt-Pt/(13%)Rh wire thermocouples in their study of the decomposition of azomethane. Similar techniques were used by Ashmore, Tyler, and Wesley to examine ignitions and slow reactions of hydrogen and chlorine in the presence of nitrosyl chloride and nitric oxide. 

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